As both complexity and miniaturization of electronic devices increase, the need for smaller size, lighter weight packaging and reliability has generated the need for connectors having the ability to reliably connect a large number of electrically conductive traces on closely spaced centerlines in compact areas. Furthermore, there are a number of electronic devices that utilize liquid crystal display units, and circuitry on glass panels and the like that cannot be electrically connected by means of individually soldered connections.
The requirements of the industry have generated a class of connectors known as elastomeric connectors, which can be disposed between circuitry on for example a printed circuit board and also on a glass panel to interconnect to corresponding circuits while avoiding the use of solder. The elastomeric member provides sufficient normal force to maintain the electrical interconnection of the circuits yet the member has sufficient compliancy so as not to damage the glass or other panels.
U.S. Pat. No. 4,820,170 discloses one such layered elastomeric connector in which succeeding layers of dielectric material and conductive material are alternated so as to provide a plurality of closely spaced but electrically isolated conductive areas. Typically the elastomeric connector is a rectangular block such that each layer is exposed on all four sides of the block, thus enabling interconnection between circuits on parallel planes or between circuits on planes that meet at essentially right angles. Since the elastomeric connector is compressible and will expand outwardly when subjected to pressure, means must be provided to support the elastomeric block in order to control the direction of expansion and maintain the block in appropriate alignment and to provide dimensioned stability for the block. In using such an elastomeric connector, therefore, a separate support housing or a special cavity within a connector housing is required. These additional parts for providing interconnection add to the number of pieces that must be molded or otherwise formed in order to achieve and maintain the desired interconnection.
U.S. patent application Ser. No. 07/407,762 owned by the same assignee as the present invention discloses a molded member having an array of compliant spring arms with conductors disposed thereon for electrical engagement with an array of conductors on the surface of a substrate. An elastomeric member is used to support the spring arm portions and to provide resistance to compression to minimize stress on the compliant spring portions and to resist the tendency of the polymeric material to "creep" and "stress relax."
U.S. patent application Ser. No. 444,577 filed 11/30/1989 and owned by the same assignee as the present invention discloses a multicircuit connector assembly for interconnecting an array of conductors of a first article with a corresponding array of conductors of a second article. The connector includes a plurality of bifurcated tines joined by a bight section, each tine having arm portions deflectable toward each other, compressible support means extending between the arm portions of the tines and continuous circuit means defined along the outer surfaces of the tine arms and bight section. The compressible support means has sufficient durometer to maintain contact normal force between the continuous circuit means and the corresponding contact means of opposed first and second electrical articles upon the arm portions being compressively held between the pair of electrical articles.
The use of compliant spring arm contact members for providing surface mounting for components to surfaces such as circuit boards is known. Typically these compliant spring arm members are made of metal that has been stamped and formed into the desired configuration.
While the metal members can be selected to minimize stress relaxation the number of manufacturing and assembly steps required to make a connector with metal members are greater than those associated with the molded assembly previously described.
To obtain the proper spring and other mechanical characteristics the metal members are typically stamped from copper alloys, which are relatively hard materials. These materials are difficult to form and cause problems in stamping since they wear out the stamping tools, thereby increasing the costs of maintaining the tooling. Dead soft copper, on the other hand, is relatively easy to stamp, form and plate but the desired mechanical and spring characteristics suffer. It is desirable, therefore, to have a means for making spring contact arms that have the desired mechanical characteristics and electrical capabilities while minimizing tooling and maintenance costs.
It is desirable, therefore, to provide a means for making connector assemblies with a minimum number of parts.
It is further desirable to minimize the steps in manufacturing such an assembly.
It is also desirable to have an assembly that is relatively lightweight and compact while maintaining the desired electronic capabilities of the more complex prior art devices.
Additionally, it is desirable to have a compliant spring arm section formed essentially of dielectric material that provides sufficient compression force to maintain electrical contact with the conductors of the mating article without the need for an elastomeric support.
Furthermore, it is desirable to maintain the features of spring contacts while eliminating stamping and forming steps required for metal members thus providing a cost effective method for manufacturing.